Several methods for measuring the amount or volume of liquid contained in receptacles are in use today. Measuring the volume can be implemented in a simple way by comparing the level of the liquid to a static gauge fixed against a vertical wall of the container or against a vertical transparent gauge connected to the container and visible from the outside.
More sophisticated methods take into consideration the tendency of liquids to occupy the lowest available spaces and flatly level in a container in which they are confined. Such prior devices employ a float which is connected mechanically to a variable electric resistor, whereupon the change in the liquid level of the resistance is expressed in an appropriate electronic circuit. Other methods of detecting the level of liquid exist which utilize physical phenomena involving energy distribution such as conduction of heat and propagation of electromagnetic and mechanical waves.
German Patent Application 37 16 770 A1 discloses a device comprising a fixed pillar, flexible beam with a strain gauge, vertical float and a spacer link connected together in a trapezoid configuration to assess the liquid level in a tank. The pillar is affixed to the container, and the lower end of the float is attached to the pillar via the spacer link. The spacer link retains the float at a constant distance from the pillar, and also corrects the reading of the volume by inclination of the container. The upper end of the float is connected to a flexible beam carrying a strain gauge. Connecting the base of the float to the pillar introduces an element of error in the reading particularly when the container is tilted or in motion. Lateral forces transmitted toward the pillar are not accounted for. In addition, the float described in the patent is vulnerable to strong movement of liquid during vehicle movement such as inclination, vibration, or brake activation. Further, additional parts connected to the float such as a central fixed pillar, the spacer link and a bearing piece present complications for the correct functioning of the device. Moreover, the device is, relative to the container, very large and special skills are needed for mounting such a complex structure. Practically, there is no way to put such a device in an already existing tank.
The device employs electronic circuits in measuring devices to enable the transmission of measuring information to remote locations. These circuits have stored information as well as facilitated calculations involving quantities of liquid and changes in the quantity.
In general, measuring liquids in tanks can be a complicated task when the container has an irregular shape, or when the tank is subject to movement or variable positions such as during transport or while resting on an incline. These variances often result in liquid measurements which are inaccurate, particularly those that rely on the level of liquid in the tank to produce a measurement of volume.
The problems associated with the measurement of the fuel status in the vehicle tank are related to the reliability of existing systems to the functional requirements such as precise measurement. Most existing systems are only able to indicate an approximate quantity of fuel in the tank. In addition, the system must function when the vehicle is parked or in any static condition, and while the engine is running, and whether the vehicle is loaded or unloaded. In general problems arise in existing systems when movement of the fuel surface is caused by the engine running, during fuel replenishment, vehicle movement on a rough road, truck inclination or brake activation and other physical variances.
There has been a need therefore, for a device which provides a precise measurement and continuous monitoring of the amount of liquid in a tank regardless of the shape of the tank, its position or operating conditions of the vehicle. Further, there is a need for such a device to be capable of use with new tanks as well as being retrofit into existing tanks.